System and method for detection of a target substance

ABSTRACT

A system for the measurement of a target substance is provided including a detection apparatus and a reading apparatus. The detection apparatus, or “carrier”, includes a pyroelectric film transducer (“pyroelectric film”) and one or more reagent concentrations (“reagent deposits”) deposited on the film. The reagent deposits are adapted to react with, and thus, detect the presence of a target substance present in the local environment. Upon detection of the target substance by the reagent deposit, the reading apparatus and the pyroelectric film may be used to detect the amount of heat that can be absorbed by the reagent in response to illumination. The pyroelectric film then delivers to the reader a signal corresponding to the heat detected and the reader provides a corresponding indication of the concentration of the target substance detected.

BACKGROUND OF THE INVENTION

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/306,469, filed Jul. 18, 2001 (hereby incorporated byreference for all purposes).

[0002] The present invention relates generally to an apparatus, system,and method of detecting a target substance, such as a gas, in a localenvironment. More particularly, the invention is such a system,apparatus, and method which employs or incorporates pyroelectric filmtechnology.

[0003] It is often desirable, advantageous, or simply necessary tomonitor the environment around a work place, home, or other sites. Forexample, in many industrial environments, hazards may exist in the formof toxic chemicals. This is especially a concern when the harmfulchemicals or substances are not readily detectable, e.g., odorless orinvisible. Thus, in these environments, the air surrounding a work placemay be constantly monitored by safety personnel equipped with portabletesting equipment, including gas detectors. Alternatively, personnel maybe required to wear or carry gas detectors, such as badges whichtypically provide an visual alarm when certain levels of the harmfulchemicals are detected. In addition, monitoring equipment may bepermanently placed at strategic locations.

[0004] The above-described applications are just some of theapplications suitable for the present invention.

SUMMARY OF THE INVENTION

[0005] In one aspect of the present invention, a system for themeasurement of a target substance is provided. The system includes adetection apparatus and a reading apparatus. The detection apparatus, or“carrier”, includes a pyroelectric film transducer (“pyroelectric film”)and one or more reagent concentrations (“reagent deposits”) deposited onthe film and adapted to react with, and thus, detect the presence of atarget substance present in the local environment. Upon detection of thetarget substance, the reagent deposit is adapted for exposure to a lightemitting source. The pyroelectric film detects the light absorption ofthe reagent deposit as microscopic heating. This microscopic heatingproduces an output that is processed to derive the measurement of thetarget substance. In this manner, the pyroelectric film is used toindicate the amount of or concentration of the target substance in theenvironment. This technology is described in U.S. Pat. No. 5,622,868,which is hereby incorporated by reference for all purposes and made partof the present disclosure.

[0006] A reading apparatus is provided that is operable with a detectionapparatus described above. Such a reading apparatus includes a anoptical device on light emitting source that is operable with thepyroelectric film and reagent deposit to indicate the amount orconcentration of the target substance. The reading apparatus and thedetection apparatus may be two distinct devices or may be incorporatedinto a single device.

[0007] As used herein, the term “indication” or “indicating” shall meanmeasuring, monitoring, or otherwise visually or audibly communicatingthe detection of the target substance to the user, including themeasurement and display of the amount or concentration of the targetsubstance in the local environment or the detection of a specifiedamount or concentration of the target substance. Also, as used herein, a“reagent deposit” shall mean a concentration of reagent applied to asurface and shall not be limited to any specific shape, form, orquantity.

[0008] A system according to the invention will include a carrier havingone or more reagent deposits deposited thereon. In one embodiment, thereagent deposits are arranged in predetermined sets, with the setsprovided in containers. The system further includes pyroelectric filmpositioned adjacent the reagent deposits, and a reader operativelyassociated with the pyroelectric film (e.g., including a light emittingsource for illuminating the reagent deposit). Note that a set of reagentdeposits may consist of one reagent deposit. The system may also includea pump (or some other means of moving air, such as a fan) for moving asample of the local environment past or in the vicinity of the containercontaining the set, so as to initiate a reaction and detection of thetarget substance. Among other elements, the preferred system may alsoinclude a filter operable with the pump and/or one or more alarms forindicating the presence of a predetermined amount or concentration ofthe target substance.

[0009] In yet another aspect of the invention, a carrier of thepyroelectric film (e.g., a cartridge) is provided that is receivable ormateable with a reading device (including a light emitting source). Thecarrier or cartridge includes one or more non-exposed reagentconcentrations that are exposed upon receipt or mating of the cartridgewith the reading device such that detection of (and/or measurement of)the target substance can occur. In various embodiments of the invention,reagent deposits may be positioned in predetermined sets. A set mayconsist of a plurality of reagent deposits arranged in a row, or otherpattern. In one specific embodiment, one or more reagent deposits areencased in protective coating or casing that is pierced, or otherwisecompromised, upon receipt or mating of the carrier supporting thereagent concentrations with a reading apparatus. In this way, one ormore reagent deposits may be exposed to the environment containing thetarget substance. To facilitate the use of the carrier and the readingdevice, the reading device may be equipped with a means for piercing theencasing upon proper receipt or mating of the carrier with the readingdevice.

[0010] In a further embodiment, the reading device includes a pump andair channel or conduit. Again, upon receipt or mating of the carrierwith the reading device, a pump (or other means of moving air past thereagent concentrations) is operable to fluidly communicate with thecontainer containing the sets of reagent deposits and allow for themoving of air or sample of the local environment to the vicinity of thereagent deposits. In this regard, the carrier may be keyed with thereading device so as to position the encasing in correspondence with theair channel and pump.

[0011] The present invention is further directed to a method ofemploying the system and/or the system described. Such an inventivemethod allows for the detection and indication of one or more targetsubstances (e.g., target gas). In another embodiment, the method allowsfor the indication of the amount or concentration of the targetsubstance in real-time. Thus, in one aspect of the invention, the methodprovides for the substantially simultaneous detection and indication ofthe target substance in the local environment.

BRIEF DESCRIPTION OF THE FIGURES

[0012]FIG. 1 is a simplified schematic representation of a gas detectionsystem and apparatus according to the invention;

[0013]FIG. 2 is a simplified perspective view of a carrier suitable foruse with the system in FIG. 1;

[0014]FIG. 3A is a simplified perspective view of a second carriersuitable for use with the system in FIG. 1;

[0015]FIG. 3B is an end view of the carrier at line 3B-3B in FIG. 3A;

[0016]FIG. 3C is a bottom view of the carrier in FIG. 3A;

[0017]FIG. 4 is a perspective view of a receiver and carrier accordingto the invention;

[0018]FIG. 5 is a perspective view of a second combination of a receiverand a carrier according to the invention;

[0019]FIG. 6 is a simplified diagram of a detector tube according to theinvention;

[0020]FIG. 7A is a simplified diagram of the detector tube of FIG. 6engaged with a pump, according to the invention;

[0021]FIG. 7B is a simplified diagram of the detector pump of FIG. 6engaged with a second type of pump, according to the invention;

[0022]FIG. 8A is a simplified diagram of a third carrier suitable foruse with the system, FIG. 8B is simplified plan view of the carrier inFIG. 8A; and

[0023]FIG. 9 is a simplified diagram of a fourth carrier suitable foruse with the system.

DETAILED DESCRIPTION OF THE INVENTION

[0024]FIG. 1 is a schematic representation of a system 100 for detectinga target substance in a local gaseous or liquid environment embodyingvarious aspects of the present invention. In a preferred embodiment, thesystem 100 is operable to indicate the amount or concentration of thetarget substance that is detected. The invention is also directed to amethod of detecting such a target substance employing a combination oftechnologies and/or functions, most of which are provided by the system100 represented by FIG. 1.

[0025] As will become apparent, the present invention is adapted forvarious applications. For example, the detection system 100 hasapplications in the general chemical detection market, particularly inthe gas detection market, as a portable or field carryable gas detector.In this market, one of the more frequently used portable gas detectorscomes in the form of badges covered with reagents that reactcolorimetrically with gases in the local environment. The badges areworn by the user and can provide a visual signal, in the form of a colorchange, when the reagent is exposed to the target gas. At most, thesebadges provide only an approximate measurement of the amount of gas inthe local environment, relying on the user to compare or evaluate thedegree of color change. The system(s) 100 depicted in the Figuresprovide a preferable replacement for these badges.

[0026] In one aspect of the invention, the inventive detection system100 employs or incorporates a core detection component provided by: anoptically detectable or calorimetric detection element, a pyrolectric orother thermoelectric transducer element operatively associated with thecolorimeteric detection element, and one or more carriers or substrates40 supporting or containing these two elements (see FIG. 1).Pyroelectric film (also called polyvinylidine fluoride (PVDF) or piezofilm) suitable for use with the present invention is described generallyin U.S. Pat. No. 5,622,868 (hereby incorporated by reference). One typeof carrier 40 that is suitable for use with the inventive system is acartridge-type carrier 40 as shown in FIGS. 2 and 3. Other types ofcarriers 40 also suitable for use with various embodiments of theinvention are shown throughout in FIGS. 4-8. These other types and thecorresponding Figures are described separately below.

[0027] Returning now to the schematic representation of FIG. 1, thedetection system 100 includes a mechanism configured to receive anoutput from the transducer element 40 and to convert the output into areadable indication of the amount or concentration of the targetsubstance detected. FIG. 1 illustrates one type of mechanism—a piezofilmreader 60—that is suitable for use with the carrier 40 of the inventivedetection system 100.

[0028] The reader 60 includes an LED light source to illuminate thereagent 32. The light is pulsed with a specific frequency—approximately50 hertz. The electrical signal produced by the heat absorbed by thecolorimetric area of the pyroelectric film, is interpreted by an analogto digital converter which is then processed by a microprocessor andthen displayed as a reading. This microprocessor may have additionalduties relating to pump control, temperature and humidity compensationof the PVDF reading, reading and writing the memory chip stored in thePVDF film cartridge (as outlined in this patent), control of alarmindicators such as visual, audible and vibration devices, and readingoptional bar code on sensor and/or filter module. In any case, a readersuitable for use with the present invention is one that incorporatesmany of the basic mechanisms as described in U.S. Pat. No. 5,622,868.

[0029]FIG. 1 further illustrates the use of a pump 10 in conjunctionwith a flow sensor 14 and flow regulator 12 for drawing and thencontrolling a flow of the local gaseous environment into or across thecarrier 40. A flow filter 16 may be recommended as well in certaindemanding environments. As further explained below, the use of a pump 10in the detection system 100 allows for measurements which areexceedingly more accurate and consistent than currently provided by theabove-mentioned badges and other known detection systems.

[0030] Depending on the requirements of a particular application, thedetection system 100 may include a number of sensors, alarms and otherinstrumentation, each of which is operable with or linked to a controlmechanism 22, as shown in FIG. 1. For example, the detection system mayinclude a digital display 26 for visually indicating the concentrationof the target substance, and one or more visual alarms 28 (e.g.,flashing red LED), audible alarms 30, and vibration alarm 32. The alarmsmay be configured to activate when certain levels of the targetsubstance are detected. The detection system 100 may also include atemperature sensor 18 and a humidity sensor 20.

[0031] In several embodiments, including the embodiment depicted in FIG.4, a portable, self-contained housing 62 is provided to house or framethe piezofilm reader 60 and the various sensors, alarms, pump-relatedcomponents, and other accessories. This housing 62 also includes amicroprocessor or equivalent means for performing or controlling variousfunctions, including conversion of pyroelectric film output to areadable digital indication. This self-contained housing 62 may bereferred as to as the carrier receiving device or simply, the reader 62.In several embodiments, engagement between the carrier 40 and the reader62 also initiates sampling of the local environment and testing for thetarget substance in that sample. Also, in several embodiments, thereader 62 is adapted to be a field-carryable, portable testingequipment.

[0032] Referring now to FIGS. 2-5, the cartridge-type carriers 40depicted therein are separate from the reader 62 but is engageabletherewith during a testing operation (and detacheable therefrom foranother testing operation). FIG. 4 depicts the carrier 40 in engagementwith a flip-top type reader 62. FIG. 5 depicts another cartridge-typecarrier being disengaged from a second type of reader 62.

[0033] The carrier 40 preferably employs a colorimetric detectableelement in the form of reagents 32 that selectively react withchemicals, or target substances, in the gaseous environment. Thereagents are also characterized by the amount of light it can absorb,which translates to microscopic heating generated within the reagent.Thus, the reagent may be illuminated with an LED to cause heat to begenerated within the reagent. In turn, a pyroelectric film transducer isemployed to measure the voltage change across the reagent which directlycorresponds to the heat generated. Upon exposure to the targetsubstance, the reagent deposit undergoes a color change, and as a resultof the color change, the reagent deposit's capacity to absorb light alsochanges. Thus, the reagent deposit may be illuminated before and after atesting operation and the corresponding calorimetric change and thedifference in the heat generated in the reagent calculated. Thecalculated voltage change is then translated into a correspondingconcentration of the measured gas (“target gas”) by the reader 62.

[0034] In one aspect of the invention, the system 100 provides for thepyroelectric film transducer/reagent to be re-set or baselined. Thismeans that, after a detection of the target substance and correspondingcolor change in the reagent, the reader stores voltage measured afterthe reagent is illuminated by a given LED. In this way, if a subsequentLED illumination does not result in a larger amount of heat beingdetected (i.e., because of no further colorimetric change in thereagent), the output signal may be recognized as the same as thatreceived in the previous illumination, and thus the reader will notindicate erroneously that the target substance has again been detected.On the other hand, if additional exposure caused the reagent to furtherreact colorimetrically, then the voltage measured would be different andthe difference in voltage can be used to indicate the concentrationdetected.

[0035] The above-described resetting or baseline method is just oneexample of a suitable method that allows the reagent to be repeatedlyilluminated and exposed a plurality of times. In each case, the system100 effectively stores in memory the amount of heat (or correspondingvoltage) that a reagent absorbs in response to an LED illumination. Thisallows the reagent to be reused, and be used longer in the field. Thisalso allows the system to discriminate between different degrees ofexposures. It is important to note, however, that the resetting orbaselining described above requires the reagent to be non-reversible(does not revert back to its original color).

[0036] In yet another aspect of the inventive testing method, anon-reversible reagent/pyrolectric film is used in combination with acontinuously running pump. The pump is operated to continuously samplethe local gaseous environment while the LED of the piezoptic reader isactivated to illuminate intermittently. Whenever a target substance isdetected, causing a colorimetric reaction and subsequent reading of theconcentration detected, the reagent/pyrolectric film is reset orbaselined. In this manner, the system 100 may be used for continuousmonitoring in the field and for multiple exposures.

[0037]FIG. 2 provides the basic structure of a carrier 40 for use withthe system 100 according to the invention. The carrier 40 of FIG. 2includes a plurality of colorimetrically-reactive reagent deposits 32deposited thereon. Different types of reagent deposits 32 may beselected such that one testing operation can detect a correspondingplurality of target substances. The reagent deposits 32 are preferablyarranged in predetermined sets 32 a. In one preferred embodiment, thesystem 100 includes a series of distinct reagent deposits 32 provided inthe same set 32 a, such that several target substances may be tested atthe same time. Alternatively, a predetermined set 32 a may consist ofone reagent deposit (see e.g., FIG. 3a).

[0038] The carrier 40 further includes a pyroelectric film transducer 42on which the reagent deposits 32 are deposited. The reagent deposits 32may be deposited directly on the pyroelectric film transducer 42 usingan ink jet printer or a screen print system. The pyroelectric filmtransducer 42 has a top surface 36 and a bottom surface 38. Inembodiment of FIG. 2, the top and bottom surfaces 36, 38 provide theelectrodes by which an electrical signal may be outputted from thecarrier 40.

[0039]FIGS. 3a-3 c depict a variation of a carrier 40 according to theinvention. To facilitate description, the cartridge 40 of FIG. 3 isshown with only one reagent deposit 32. The reagent deposit 32 iscontained or housed within an initially sealed tunnel 34, as best shownin end view of FIG. 3c. The tunnel 34 is essentially an elongatedconduit extending the length of the cartridge 40 providing for fluidcommunication between the pump 10 and the local gaseous environment.Preferably, the tunnel 34 also contains a filter 58. The tunnel 34further includes an inlet end 34 a and an outlet end 34 b, whichprovides a conduit for passage of the sampled gaseous environment. Theinlet and outlet ends may be sealed by a plastic film or the like. Asfurther described below, upon engagement of the cartridge 40 with thereader 62, the sealed inlet end 34 a and outlet ends 34 b aresimultaneously punctured, thereby creating the fluid conduit andallowing for exposure of the reagent 32.

[0040] Referring to the end view of FIG. 3b, the pyroelectric filmtransducer 42 is provided as a mat situated along the bottom portion ofthe tunnel 34, thereby providing a bed or support for the reagent 32. Inone variation of the cartridge 40, the cartridge 40 is made of glasssuch that the bottom surface on top surface of the tunnel is sealed by aglass surface. In further embodiments, the top end may be sealed by aplastic film.

[0041] Now referring to the bottom view of FIG. 3c as well, the carrieror cartridge 40 also includes an embedded memory chip 52 with leads orpins mateable with the reader 62. The memory chip 62 may be used tocommunicate the characteristics of the reagent 32 dot as well as thetesting protocol or procedure for the target substance. The bottom viewof FIG. 3c also shows lead lines 54 and connectors extending from thepyroelectric film. The connectors are situated so as to be mateable withcorresponding connections on the piezoreader 60. Further, the cartridge40 is also provided with a key/alignment hole or pin 56 for aligning thecartridge 40 with a corresponding hole or pin of the reader 60.

[0042]FIG. 4 shows the cartridge of FIG. 3 engaged within a receivingcompartment or bay 66 of the fliptop reading device 60. When properlysituated in the compartment, as provided by aligning the key alignmenthole with the corresponding key alignment pin of the reader, theconnectors 54 for the pyroelectric film 42 and those for the memory chip52 align with and connect with corresponding connections on thepiezoreader 60. Moreover, the inlet and outlet ends of the tunnel 34 ofthe cartridge 40 align with corresponding conduits integrated with thereader 62. Moreover, a tab device provided on the compartment may bepositioned so as to puncture the inlet and outlet ends 34 a, 34 b. Inthis way, operation of the pump 10 draws a sampling of the local gaseousenvironment through the tunnel 34, thereby exposing the reagent 32 andinitiating a colorimetric change therein. FIG. 4 also illustrates theuse of a pump 10 having a pumping conduit 10 a connecting the cartridgewith the pump 10, and also with the sampling inlet 10 b and outlet 10 c.

[0043] The display 26, shown in FIG. 4 is a standard LCD display, andmay be alphanumeric or graphical depending on what information isnecessary to display. The display 26 provides the user with a numericindication of the measurement of the concentration of the targetsubstance (either direct immediate exposure or long term dosimeterreadings). The display 26 may also display text and graphics of alarms,menus for device settings including alarm points, time, date,data-logging, gas name, sensor name, and filter name.

[0044] The pump 10 may be a fan, air pump, or other device that iscapable of moving air. The pump may be located on either the intake airpath before the reagent or located in the exiting air path. The pump 10may be operated continuously or intermittently, or may be turned on fora specific amount of time for purposes of obtaining a reading or tominimize power consumption. Alternatively, the pump may be known tooperate at a specific flowrate.

[0045] In the preferred embodiment of the invention, the pump 10 is usedwith the flow regulator 12. If the invention did not employ a flowregulator 12, the pump would be used as an uncontrolled air source thatwould indicate the presence of a gas, but the measurement of the amountof the target gas would not be as accurate as a measurement taken with aflow regulator 12. The flow regulator 12 can either use feedback fromthe motor or from the flow sensor 14. A preferred method is to controlelectrical power to the pump device with a feedback from the flowsensor. Such regulation may consist of controlling the pump speed and/orthe on and off time of the pump in either a pulsed fashion or on for aspecific time period. The flow regulator consists of an electric circuitthat interfaces with the flow sensor 14 (or motor feedback) and providespower to the motor directly.

[0046] The inventors have discovered that the use of a pump 10 incombination with calorimetric and pyroelectric technology providescertain benefits. For example, the use of a pump speeds up the reactiontime of the reagent and allows for a virtually instantaneous measurementof the level of the target substance in the local environment.

[0047] Furthermore, precise control of the pump, as in the presentinvention, provides measurements exceedingly more accurate than isachievable with prior art systems and methods. This achievement by theinventors stems from the understanding that the discoloration or stainproduced by the calorimetric reaction in the reagent is proportionallyrelevant to the amount of air or gas that is contacted with the reagentsurface. With prior art colorimetric reactions, the air or gas iscontacted with the reagent through simple diffusion—which has to betimed in order to provide an acceptable, accurate measurement. In thepresent inventive system and method, the flow rate of the pump can bemeasured and/or controlled, as well as the pumping duration, and thus,the amount of air or gas contact with the reagent can also be measuredand/or controlled. As a result, a high level of accuracy in measurementscan be achieved and repeated. Moreover, use of the pump to initiate orencourage contact provides higher precision than the use of simplediffusion because the diffusion rate is typically affected and varied byexternal conditions, including wind.

[0048] In certain embodiments, a measurement device may be used tomeasure the amount of local environment delivered by the pump. If thepump 10 operates at a known flowrate, the measurement device couldconsist of a timer to time the length of operation of the pump and aconverter to convert the flowrate and the pump operation time to avolume of local environment delivered. The flow sensor 14 may beprovided as the optional measuring device to provide feedback to theflow regulator 12. The preferred method of flow sensing employs adifferential pressure sensor. A wide range of sensors, includingelectromechanical sensors, hot wire sensors, and many others can beused.

[0049] Further, the reader 62 preferably includes a circuit board orother support 70, which includes the piezoptic reader 60, as well as thecontrol mechanism 22. When the cartridge 40 is received in the bay 66,it is situated over the board 70, and such that LED's provided on theboard advantageously align with the reagents 32. In further embodiments,multiple LED of various colors may be employed in combination with alight pipe for selectively illuminating the reagent with a variety oflight sources. The board 70 also includes contacts for the memory chip52 such that reagent information and testing requirements may becommunicated to the reader 62.

[0050]FIG. 5 depicts yet another reader 162 and carrier 140 combination,according to the invention. The carrier 140 is shown being disengaged ordetached from the receiving bay 166 of the reader 162. The carrier 140includes one or more containers 110, each containing a set of reagentdeposits 132. Preferably, the container 110 is a channel that isparticularly adapted to fluidly communicating the local environment withthe selected set of reagent deposits 132.

[0051] In one embodiment, the carrier 140 may be fed into the reader 162by an electric motor. In another embodiment, the carrier 140 may be fedthrough operation of some type of ratchet or manually fed by hand. Thecarrier 140 may be made of a firm, durable plastic and may contain abarcode, magnetic stripe or embedded memory chip to identify thespecific carrier 40 and the target substances and ranges it is capableof detecting.

[0052] The system further includes a means for selecting or designatinga predetermined set of reagent deposits 132 for exposure to the localenvironment containing the target substance. In this manner, the userdetermines what target substance(s) to test for. Upon engagement of thecarrier 140 with the reader 162, the selecting means penetrates thecontainer 110 containing one set of reagent deposits, thereby exposingthe selected reagent deposits to the local environment as furtherdiscussed below.

[0053] The system 100 embodies a reagent deposit 132 which due to itslimited quantity is easily and quickly reacted upon exposure to air andhumidity, causing a short “shelf life.” In another embodiment, eachcontainer 110 containing a set of reagent deposits 132 is covered by ashield 130, shown in FIG. 5 as a tunnel, to shield the reagent deposits132 from the local environment until the carrier 140 is engaged with thereader 162. Upon engagement of the carrier 40 with the reader 60, theshield of the selected set of reagent deposits 132 is penetrated orcompromised, allowing exposure of the selected set of reagent deposits132 to the local environment containing the target substance. The tunnelis preferably made of glass, but could also be made of another rigidmaterial such as mylar or polyvinylchloride. The ends of the tunnel arepreferably covered with film that may be compromised or punctured toexpose the container 110. Alternatively, the shield 130 could consist ofa film covering each container 110. In one aspect of the invention, theshields (either in the form of a film covering or a tunnel) allow formultiple testing procedures using the same carrier 140. During a testingoperation only the selected set of reagent deposits 132 are exposed,leaving the remaining sets of reagent deposits unexposed underneath theshield. The shield-compromiser preferably consists of a sharp implementto puncture the film-covered ends of the tunnel or the film.

[0054] In another embodiment of the invention, a filter is used tofilter out interferences from the local environment containing thetarget substance before the local environment comes in contact with theselected set of reagent deposits. Filters generally improve thespecificity and accuracy of the colorimetric and target gas interaction.The filter may be a variety of materials and coatings to specificallyfilter interferences (through membranes that restrict particle size,chemicals that react with, remove, or change a chemical compound intoanother chemical that will not interfere with the target gases) from theselected set of reagent deposits. Specific filters could include ahydrophobic filter to remove humidity, a filter to screen out tolueneand xylene from benzene and air, a filter to remove chlorine gas from amixture of chlorine dioxide and air, and many others.

[0055] These filters may be used individually or in combination asneeded to filter interferences from the selected set of reagent deposits23. Further uses of such filters will be apparent to one skilled in theart upon review of the present disclosure.

[0056] One kind of filter that may be used is a column or a long glasstube is coated with a substance that temporarily bonds with specifictarget substances. The temporary bonds are subsequently released whenheat is applied to the column. Because of the temporary nature ofchromatographic columns, this type of filter is preferably used in theportable embodiment of the system, but not the fixed embodiment. Thistype of filter has the advantage of temporarily holding back theinterfering substance during the measurement of the primary targetchemical, but then allowing the measurement of the interfering substancewhen it is released from the column when heat is applied.

[0057] In yet another aspect of the invention a specific type of filteris designed to change the target compound into a gas that will have acalorimetric reaction. This is accomplished by a providing a chemicallayer that reacts with the target substance and changes, through achemical reaction, the target substance into a gas that then reactscolorimetrically with the reagent deposits on the pyroelectric filmsensor strip. This can be accomplished with many target compounds,including methyl bromide, which is broken into bromine through reactionwith sulfuric acid. The bromine then reacts colorimetrically with thereagent deposits, such as o-tolidine, on the pyroelectric film sensorstrip to produce a yellow color. There are some chemicals, which arereacted in as many as three or four phases of such reaction filters toproduce the final product which is measured by a calorimetric reactionwith the reagent deposits.

[0058] Like the pump, the filters can be engageable with the container110 containing the selected set of reagent deposits. The filters couldoptionally be stamped with a bar code such that they may be recognizedby the reader 162 with a barcode reading device. This would allow thereader 162 to compensate, or report to the user the use of the filter orthe lack of presence of the filter. Furthermore, the filters couldoptionally be constructed in such a manner that the filter itself wouldcontain or be made of a calorimetric substance that would cause a colorchange of the filter material showing that the material is beingconsumed or that it has been fully consumed.

[0059] As previously mentioned, the cartridge is mateable with and thendetachable from the reading apparatus. When keyably engaged with thereading apparatus, the air channel, cartridge channel, and outlet arefluidly aligned so as to allow for the passage of pumped airtherethrough. Alternatively, the reading apparatus may be equipped witha key or piercing mechanism for piercing film sealably applied to theends of the cartridge channel. Thus, upon proper receipt of thecartridge in the cartridge bay, the reagent deposits may be exposed withan air sample from the local environment. Accordingly, detection andindication of the target gas can occur immediately.

[0060] One method employed to “open” or “pierce” the cartridge providesfor the unit to contain two hollow pins which are sufficiently long topuncture the bottom of the cartridge at each end providing an air paththough the puncture pins themselves. Due to the possible manufacturingdifficulty of puncturing the cartridge, one preferred method ofcartridge construction would entail a cartridge as shown in FIGS. 3-5.This would be the composite of two plastic plates that, when joinedtogether form a “credit card” shaped plastic device with a hollowinterior forming a tunnel or channel through the middle of the device.Prior to assembly of the opposing halves of the cartridge, the embeddedpieces would be placed inside the device, then both pieces would beassembled and sealed possibly with a heat seal or a glue.

[0061]FIG. 6 depicts yet another embodiment of the invention. In thisembodiment, a detector tube 206 is employed to support the carrier 40during storage and testing. The detector tube 206 is ahermetically-sealed glass tube, structurally similar to thosecommercially available in the industry. The detector tube has abreakable inlet end 206 and a breakable outlet end 208. The carrier ofFIG. 6 includes three reagents spots 232 supported on a polyelectricfilm transducer 242 and filter material positional upstream thereof. Thecarrier further includes two wire lead lines 212 that are directedthrough the walls of the glass tube, thereby providing two electricalconnections for a reader.

[0062]FIGS. 7A and 7B depict the detector tube 206 operated with abellows pump 210 a and a manual pump 210 b. Either pump may be used incombination with the detector tube 206 to conduct a field testingoperation. In particular, the detector tube ends are broken and insertedor engaged with the pump, thereby drawing a sampling of the localenvironment through the detector tube and past the reagent. Thus, if thereagent is exposed to the target substance, a colorimetric changeoccurs. The detector tube is then disengaged from the pump and engagedwith the appropriate reader such that the connections 212 mate withcorresponding connections in the reader. Upon engagement with thereader, one or more LEDS on the reader may be operated to illuminate thereagent (through the glass wall).

[0063]FIGS. 8A and 8B depict yet another variation of a carrier for usewith the system according to the invention. In particular, FIG. 8depicts the use of a reel-to-reel tape mechanism 306 for sealinglystoring and dispensing individual carriers 340. As shown in FIG. 8B, thereel tape may be segregated into distinct sections, including a sectioncomprising a carrier 340. The carrier will include polyelectric filmtransducer 342 and one or more reagent deposits 332 thereon.Conveniently, the tape acts to seal the reagent 332 before the reagent332 is exposed during unwinding, thereby eliminating the need for asealed container or tunnel. Accordingly, one benefit of the embodimentof FIGS. 8A, 8B is that it allows for “long term” measurement, whilepreserving the life of the unused reagents.

[0064] The roll of tape may include various combinations of reagents oronly one type of reagent. Further, the reel-to-reel mechanism may bemounted or housed integrally with a reading device. In the alternative,the reel-to-reel mechanism may be integrated with a fixed testingmechanism rather than a field carryable portable gas detector.

[0065]FIG. 9 depicts yet another variation of a carrier for use with thesystem according to the invention. The carrier of FIG. 9 is a disk typecarrier 440 preferably holding a plurality of reagent deposits 432. Thereagent deposits 432, as before, will be deposited on and supported by amat of polyelectric film 442. The polyelectric film 442 may beindividual mats or a continuous, circular sheet of film, as shown inFIG. 9.

[0066]FIG. 9 also illustrates a reagent deposit sealingly situated in atunnel 434. The tunnel 434 includes fluid communication inlets (notshown) and outlets 436, which are penetrated and unsealed uponengagement of the disk carrier 440 with the appropriate reader. Forexample, in FIG. 9, only one reagent deposit remains unsealed, but ispositionally engaged with the reader so as to be in alignment with thepumping means provided by the reader. When aligned and in operation, thepump may be operated to draw air from the periphery of the tunnel andpast the reagent, towards the center of the disk carrier 440. Uponconclusion of a testing operation, the disk carrier 440 may be rotatedso as to align yet another reagent deposit for a subsequent operation.As before, the tunnel 434 may be covered by glass or film, with the endspreferably covered by a puncturable film sheet.

[0067] Although the present system, apparatus and method of detecting atarget gas and its advantages have been described in detail, it shouldbe understood that various changes, substitutions and alterations can bemade herein without departing from the spirit and scope of the inventionas defined by the appended claims. Moreover, the scope of the presentapplication is not intended to be limited to the particular embodimentsof the process, machine, manufacture, composition of matter, means,methods and steps described in the specification. For example, variousexemplary configurations of a detection apparatus and a readingapparatus have been described. As one of ordinary skill in the art willreadily appreciate from the disclosure of the present invention, variouselements from measurement or instrumentation technology, or measuringmethods or steps, presently existing or later to be developed thatperform substantially the same function or achieve substantially thesame result as the corresponding embodiments described herein may beutilized according to the present invention. Accordingly, the appendedclaims are intended to include within their scope such machines,apparatus, methods, or steps.

What is claimed is:
 1. A system for measuring the concentration of at least one target substance, said system comprising: one or more carriers, at least one of said carriers having a plurality of reagent deposits thereon, said reagent deposits being arranged in a plurality of predetermined sets, containers wherein each of said sets of reagent deposits is contained, and pyroelectric film positioned adjacent said reagent deposits, said pyroelectric film being adapted for detecting heat absorbed in said reagent deposit and correspondingly delivering an output signal; and a reader engageable with said carriers and operable to initiate a measurement of the concentration of at least one target substance by exposing a selected set of reagent deposits, said reader being adapted to receive the output signal from said pyroelectric film to convert the output signal into a concentration of the target substance, wherein said carrier is detachable and re-engageable with said reader to initiate exposure of a second set of reagent deposits in a second container.
 2. The system of claim 1, wherein said carrier includes a set of reagent deposits having a first reagent deposit for measuring the concentration of a first target substance and a second reagent deposit for measuring the concentration of a second target substance.
 3. The system of claim 1, wherein said carrier includes a first set of reagent deposits including a first reagent deposit for measuring the concentration of a first target substance and a second set of reagent deposits including a second reagent deposit for measuring the concentration of a second target substance.
 4. The system of claim 1, further comprising means for selecting one of said sets of reagent deposits for exposure to the environment.
 5. The system of claim 4, wherein said container includes a cover for sealing the reagent deposits from the environment, and wherein said selecting means includes means engageable with said cover, upon engagement between said carrier and said reader, so as to expose a selected set of reagent deposits.
 6. The system of claim 5, wherein said selecting means includes a memory chip included in said carrier.
 7. The system of claim 4, said system further comprising: a plurality of filters selectively engageable with one or more of said containers for filtering interferences from the environment containing the target substance.
 8. The system of claim 1, said system further comprising: a plurality of filters selectively engageable with one or more of said containers for filtering interferences from the environment containing the target substance.
 9. The system of claim 1, wherein said reagent deposits are deposited directly on said pyroelectric film.
 10. The system of claim 5, wherein said container includes two ends and said cover being positioned to cover said two ends.
 11. The system of claim 1, further comprising: a pump selectively engageable with one or more of said containers such that the environment containing the target substance can be passed through a selected container.
 12. The system of claim 11, wherein said pump is continuously operable, said reader includes an optical device intermittently operable to illuminate at least one of said reagent deposits.
 13. The system of claim 1, further comprising a rollable tape holding said one or more carriers, said tape being sequentially advanceable so as to expose a reagent deposit.
 14. The system of claim 12, wherein said rollable tape is provided on a reel-to-reel mechanism, and wherein one of said reels is provided to support a roll of unused carriers, such that said unused carriers are sealed when supported thereon.
 15. A system for measuring the concentration of at least one target substance, said system comprising: one or more carriers, said carrier having at least one container wherein at least one reagent deposit is deposited, and pyroelectric film positioned adjacent said reagent deposit, the pyroelectric film being adapted for detecting heat absorbed by said reagent deposit and correspondingly delivering an output signal; a reader engageable with said carrier, said reader being operable to initiate two or more measurements of at least one target substance by exposing said reagent deposit two or more times, said reader being adapted to receive a first output signal from said pyroelectric film corresponding to heat detected by said pyroelectric film and to convert the outputs into a corresponding measurement of the concentration of the target substance; and a pump engageable with said containers such that an amount of the environment containing the target substance can be passed through said selected container to expose the reagent deposit to the environment.
 16. The system of claim 15, wherein the pump operates at a known flowrate.
 17. The system of claim 16, further comprising: a measurement device measuring the amount of environment passed through said container, said measuring device being operatively associated with said reader, such that the measured amount can be accounted for in the conversion performed by the reader; a timer for timing the length of the use of the pump; and a means for converting the length of the use of the pump into a volume of environment delivered by the pump.
 18. The system of claim 17, wherein said containers containing sets of reagent deposits can be used to measure more than one environment by being exposed successively to distinct environments.
 19. The system of claim 15, wherein said reader is adapted to convert said output into a corresponding measurement of the target substance by using a known reference of output from the pyroelectric film and comparing the known reference output with output from the pyroelectric film after the reagent deposit has been exposed to the environment containing the target substance.
 20. The system of claim 19, wherein said reader is adapted to reset the known reference of output after one or more exposures of the selected sets to a target substance to the last output received from the pyroelectric film prior to converting the output from the pyroelectric film into a measurement of the target substance.
 21. The system of claim 17 further comprising means for selecting one of said sets of reagent deposits for exposure to the environment containing the target substance by selecting one of said containers upon engagement of said carriers with said reader, wherein said carrier is detachable and re-engageable with said reader to initiate exposure of a second set of reagent deposits in a second container.
 22. A method of measuring at least one target substance, said method comprising the steps of: providing a carrier having at least one container containing a plurality of predetermined sets of reagent deposits, and pyroelectric film positioned adjacent the reagent deposits, the pyroelectric film being adapted for detecting heat absorbed in a reagent deposit and correspondingly delivering an output signal; providing a reader engageable with the carrier to initiate a measurement of at least one target substance; and engaging the carrier with the reader, including exposing a set of reagent deposits in a selected container by pumping an amount of the environment containing the target substance through the selected container to expose the selected set of reagent deposits to the environment; receiving an output from the pyroelectric film; and converting said output into a corresponding measurement of the target substance by using a known reference of output from the pyroelectric film and comparing the known reference output with output from the pyroelectric film after the reagent deposit has been exposed to the environment containing the target substance; and
 23. The method of claim 22, further comprising the steps of: measuring the amount of environment pumped, and accounting for the measured amount in the converting step.
 24. The method of claim 23, wherein said measuring step comprises: accounting the duration of pump operation; and converting the duration into a volume of environment delivered by the pump.
 25. The method of claim 22, further comprising the step of repeating the selecting, exposing, receiving, converting, and pumping steps to measure another environment using a single reagent deposit.
 26. The method of claim 22, wherein said converting step includes: using a known reference of output from the pyroelectic film; and comparing the known reference output with output from the pyroelectric film after the exposing step.
 27. The method of claim 22, further comprising the step of resetting the known reference of output from the pyroelectric film after the exposing step to the last output received from the pyroelectric film.
 28. A method of measuring the concentration of at least one target substance present in a gaseous environment, said method comprising the steps of: providing one or more carriers, at least one of the carriers having at least one reagent deposit; and pyroelectric film positioned adjacent the reagent deposit, the pyroelectric film being adapted for detecting heat absorbed in a reagent deposit and correspondingly delivering an output signal; providing a reader engageable with the carrier and operable to initiate a measurement of at least one target substance by exposing the reagent deposit; and engaging the carrier with the reader, thereby exposing the reagent deposit; and operating the reader to receive the output signal from the pyroelectric film and converting the output signal into a corresponding measurement of the concentration of the target substance in the environment;
 29. The method of claim 28, further comprising the steps of: disengaging the carrier from the reader; and repeating the selecting, engaging, and operating steps.
 30. A system for measuring the concentration of at least one target substance, said system comprising: a detector tube including a carrier, said carrier having at least one container wherein at least one reagent deposit is deposited, and pyroelectric film positioned adjacent said reagent deposit, the pyroelectric film being adapted for detecting heat absorbed by said reagent deposit and correspondingly delivering an output signal; a reader engageable with said detector tube and said carrier, said reader being operable to initiate measurement of at least one target substance by exposing said reagent deposit, said reader being adapted to receive a first output signal from said pyroelectric film corresponding to heat detected by said pyroelectric film and to convert the output into a corresponding measurement of the concentration of the target substance; and a pump engageable with said containers such that an amount of the environment containing the target substance can be passed through said selected container to expose the reagent deposit to the environment. 